Fourdrinier wire cloth



Jan. 26, 1965 H. s. HILL 3,167,281

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United States Patent 3,167,281 FOURDRZINEER WIRE CLGTH Herbert S. Hill, Westfield, Mass, assignor, by mesne assignments, to Cheney Bigelew Wire Works Inc., Springfield, Mass, a corporation of Deiaware Filed June 13, 1962, Ser. No. M92398 3 Claims. (Cl. 245-8) The present invention relates generally to new and useful improvements and structural refinements in wire cloths for use in papermaking machines and is directed more particularly to the provision of stainless steel warp strands and non-iron weft strands in the formed woven wire cloth or belt.

It will be helpful to an understanding of this invention first to briefly consider some of the history of the prior art as it reflects upon the essential points and more important features and aspects hereof so that same may be kept in mind during the subsequent reading of the detailed description of the practical embodiment of my improvements and illustration thereof in the hereunto annexed drawings.

The wire cloth or belt, as in the case of Fourdrinier machines, as is well known, is in the form of a continuous band of fine wire mesh which moves over spaced supporting rolls and in contact with suction boxes and roils. In modern machines, the increased width of the machines, the increased speed at which the machines 0perate, and the greater number of table rolls, all have been such that a belt, which would stand up for a normal period upon an older type of machine, now frequently fails due to fatigue.

In order to provide strength and flexibility to meet these modern conditions, cloths have been woven with I heavier sizes of wires in which the weft count is reduced because of the impossibility with these heavier sizes of obtaining a fine beat up of the weft, all with the result that the mesh openings become increasingly greater in the longitudinal direction of the wire.

In an ordinary Fourdrinier wire construction, standard wires are made of 60 to 100 mesh, the 60 mesh wire usually having 60 warp wires and 40 weft wires to the inch, and the 100 mesh wire having 100 warp wires and 86 warp wires to the inch, the intermediate sizes being proportionate.

While greater strength has been obtained, a number of objections are inherent in these belts, among which may be mentioned, the roughness of the paper formation surface which produces deep depressions in the paper and the tendency of the fibers to turn down into the mesh openings. Of this later objection, it is to be mentioned that the fibers of stock used in making paper, when running on a wire, tend to turn down into the mesh openings, particularly where the opening is longer in the longitudinal direction of the wire, causing a clogging, unevenness of. the sheet, and loss of stock. These problems are accentuated by the circular cross-sections of the wires 7 which provide natural diverging entrances to the mesh openings. The finer beat up of the shute wires permitted according to my invention and the fiat surfaces of both the warp and shute knuckles, overcomes these objections, the fibers being so supported that they bridge the mesh openings rather than turn downwardly thereinto as heretofore.

Desiderata in woven wire cloths are that they: (1) be capable of longer life in the face of the concomitant fact that machine production speeds are ever on the increase; (2) offer improved wear surfaces with the warp and shute knuckles disposed in the same planes; (3) be more flexible in the longitudinal direction of the cloth so as to I withstand alternating strains and stresses; (4) be relative- Ice 1y thin so as to offer improved drainage due to the obvious fact that the higher speed of rotation of the cloth dictates, inversely, a shortening of the time during which the papermaking fibers may be oriented in the aqueous suspension deposited upon the wire; (5) offer fabric structures which will emboss notwithstanding the omnipresent factor that, with the higher operating speeds, the pressing of the fibers against the wire structure follows with greater force due to the increase in the pull of the suction boxes, such increase being dictated in order sufficiently to thicken the increased amount of web forming material; (6) offer a reduction in wire fatigue due to rapid flexing; (7) oifer a means whereby paper formation is as flat as possible while nonetheless allowing adequate drainage; and (8) allow maximum resistance to abrasion experienced during the wire weaving fabrication and subsequently in its operational use.

Because of the plurality of factors intertwined in the above itemized desiderata, the paper sheets produced on these present-day faster-operating machines exhibit strong patterning or marking by the wire cloths employed as compared with the patterning produced, when and if lower operating speeds are maintained, which patterning or marking is obviously detrimental to the quality of the end product.

Paper machine wire cloth has heretofore and long been woven from warp wires and shute or weft wires, composed normally of metals such as bronze and brass respectively, and as such has performed reasonably satisfactorily in the past, although it has exhibited alarming and aggravating tendencies to wear out rapidly due to the severe abrasive action as it passes over the surfaces of the suction boxes of the paper machine.

Particularly where the warp wires of such a wire cloth have been formed of bronze, same have been unable adequately to accommodate themselves to offset, inasmuch as they exhibit undesirable tendencies toward elongation, a tendency which is overcome by the con struction of the present invention.

Even more particularly, when the shute wires are formed of ferrous materials, diiiiculty is experienced in arranging the shute wires on a plane parallel with the warp wires. Such disadvantageously affects the weaveability of ordinary wire cloth alloys and the smoothness of the surfaces of the formed end product.

On the other hand, Wire cloths made of stainless steel warps and wefts have also been known but they suffer the disadvantage of insufficient lock up between the warps and wefts, considerable work hardening at the knuckles being experienced. Another salient objection to all-stainless steel cloths lies in the inability to allow the desired crimp at the knuckles, there being relatively little dis placement of the metals thereat.

With these problems and others in mind, I have devised a novel means whereby these aforedescribed difficulties and objections are overcome to a greater degree than has heretofore been possible. I provide improvements in the art of paper machine wire cloths aiding in the solving of the difficulties involved and particularly assuring a longer wire cloth life and the prevention of the previously alluded to objectionable markings, it being one desideratum that the woven wire be smoother upon its opposite planar surfaces, and another, that it be of a lesser thickness in order that the papermaking fibers will be pressed to a lesser depth into the Wire openings.

In this invention, I particularly propose to utilize stainess steel warp wires (laid together in parrallelism as pairs) in the horizontal plane or" the woven wire cloth and to weave these with weft or shute wires (formed of a softer non-ferrous metal) in manner wherefore a smoother surface on the top of the wire cloth contributes effectively to the formation of an improved sheet.

The employment of warp wires in pairs, or side-by-side relationship, will permit of a flatter type of weave,.that is, a decrease in the thickness dimension without any sacrifice of strength, wherein the weft knuckles will provide larger surfaces contiguous to the paper formation and wear sides,

wires, the warp wires will undergo less deformation in the crimping than do the more flexible weft wires, and at the same time, the knuckle surfaces may be brought in the plane of the plane of the warp wire knuckles. 'Also, these so that the cloth will have a longer life by virtue of a smoother upper planar surface on'the working or top surmachine with stainless steel warp strands, said strands being laid .in pairs in close contact. with each other in the face of the .wire and an improved wearing surface on V plane of the wovenwire and each being of a certain minimal diameter, and with soft non-ferrous weft strands, said strands likewise being laid in theplane of the woven wire and each being of a diameter greater thanthe said certain minimal diameter.

Each warp wire of circular cross-section is a few thousandths of an inch in diameter, and the spacing between adjacent pairs of warp wires is also a few thousandths of an inch. Contrariwise, the weft wires, also of circular cross-section, are preferably larger in diameter than the warp wires, it being acknowledged that in many instances,

the weaving operation may cause .them to assume an elliptical or .fiattened cross-section at the knuckles.

Due .to the flat shape and relative thinness of the warps,

the cloth may be .beat up to a much finer mesh than has heretofore been possible with single warp wires of. the necessary strength. 7

The invention has application both in regular weave wires and in twill weave wires where the warp wires are carried under two andoverone'weft wire to provide longer knuckles and greater wearing surface at the under side. In the case of twill weave .wires, the relatively large paper formation and wear surfaces of the warp and weft wires willmake for a much finer paper. formation surface, as distinguished from the usual types .of twill weave'wires in which the paper formation surface offers long deep depressions due to the spacing of the warp knuckles to every third weft wire instead of to every sec- 0nd weft wire as in the regular .weave. By increasing the lengthof theweft knuckles, and, at the same time,.by obtaining a finer beat up due to the ribbon like warp wires, the depressions are not only decreased in size, butthe walls of the meshopenings have less convergence, all so as to allowbetter support for the paper fibers with a decreased. tendency for said fibers to. turn down into the mesh openings. 7 p

According to one aspect of the invention, there is an increase in the weft knuckle surfaceslboth in the direction of the weft wiresandin the direction of the warp wires the increase inthe direction of the weft wires being. due. to. the formation of the weft knuckles over the flat warp wires, and the increase in the direction of warp wires being due to the increased dimension of the'weft wires in the direction of the warp, as dist-inquished from. the single circular. cross-section warp wires heretofore employed warp wires ,up to thesurface of .the cloth.

' weft knuckles, due to their being. formed over pairs of warp wireswill present substantially flat paper contact and wear surfaces, there being a greater weft knuckle surface contiguous to the plane of the projected warp knuckles than would be the case if the weft knuckles were formed about single, circular cross-section, warp wires.

By providing an increase in the size of theknuckles, a greatly increased wearing surfaceis produced which will remain uniformthroughout a longer wearing life. I permits the top knuckles of. the .weft wires to be close to the plane of'the top knuckles of the warp wires, so that the fibers of the paper web have twice as many supports as with ordinary wire cloth wherein only the warp knuckles support the. fibers. 1

With the. longitudin'ally-extending warp wires being .as thin as is possible, they allow offsetting of the transversely-extending.weft wires to an extent such that their offset peaks will contact-the surface line of thewarp wire. peaks.

The weft. wires are crimped at the under side of the cloth in manner so that the bottom knuckles of the-weft wires are spaced upwardly a substantialdistance from the plane ofthe bottom-face of the cloth, wherefor the warp wires thus receive the wear and the weft wires are not weakened by said wear.

The variationof the crimp between the top and bottom sides of the cloth can be regulated'by the set of the loom in a manner well knownto the, artby merely providing a different degree of tension for the upper and lower wires of the. shed. By so adjusting the tensions that the top shed does not'have as much tension as the bottom 'shed, the shute wire is thrown to the top of the cloth with the, resulting.diiferenceinf degreeof crimp thereof, its bottom knuckles receiving a'deeper crimp than its top knuckles. j v V By the combination"v of wires of contrasting materials and the hardness differential thus offered, the softer nonferrous weft Wires are fully offset by the transverselyarr anged, relatively-more-tough, ferr'ousfstainless steel That is to say, by thecoaction of. th '.'wires of ferrous and nonferrous materials, I achieve a superiordegree of deformation through improved mechanical fusion, meaning a locking of a harder warp wire against a softershute wire where theharder metal of the warp exhibits a capacr ofthewarps and wefts are similar, the desired coaction due, to the difference in the hardness. thereof is not ,ity to force. the shute up into the plane of the .warp

knuckles; V I i Contrariwise, wherethe' actual ingredients of the metals realized.

Only by such use of dissimilar metals can these allimportant problems of true plane and correct'drainage be solved insuch successful degree, and same is. attributed primarily to the differences in size of the warp and weft As earlier reverted to, heretoforethe crimp of the weft wires, particularly where the Warp' count was high, was

i not great enough to bring the weftxknuckles'up to or. near the plane of the warp knuckles, wherefor depressions were provided atthenpper wire surface whichprodueed roughness .in the paper. Further, at the wear side, the weft 7 knuckles'wouldnot provide any substantial wear surfaces,

the wear being almost entirely confinedto the warp knuckles. f

Too, in prior artcloths, the amount of crimp obtainable with weft wires has been limited, and when it has been attempted to use a weft wire smaller in diameter than the warp wire, in order to increase the crimp, the weft wire I has been susceptible to being cut'orflotherwjse damaged.

By the invention hereof, .I olferi an improved crimping of the weft wires. ..Due .to the relative thinness of the warp fwires, as compared to the diameters of the weft wires which allows the aforesaidimproved locking action and to the fact that the entire thickness of the width less, it now being possibletobring the shute wire up nto a tighter .wire with the'stainless' steel 'warp wires taking, littleof the mechanically-created stresses during weaving and with the non-ferrous. weft wires taking the majoritythereofr This last-mentioned feature is evidenced by'the deformation into more or less egg-shape which 7 steel wires of'reduced diameters, the combined diameters of a dual strand being less than the diameter of any standard monofilament warp wire heretofore used, so as to contribute to the relatively smaller'cross-sectional di- This ,mension of the wire hereof as contrasted with prior art cloths.

The pairs of thinner warp wires, as contrasted with the usual thick single warp wires, significantly allow a cloth of reduced cross-sectional thickness so as to effectuate a general flattening of the wire surface, and of extreme ductility capable of taking the bends, encountered with the faster-travelling wires of todays paper machines, with a greater degree of facility than has ever before been experienced. That is, the bending movements are adsorbed in greater degree than has heretofore been possible.

The stainless steel of the warp wires does not work harden so as to prove detrimental in operational use, and further, by means of the combination of warp wires in parallelism, I do not deform the relatively smaller strands.

The intersecting stainless steel warp strands will have little or no contact with the surfaces over which the wire travels, thereby greatly reducing the abrasive action between the surfaces of the warp and weft strands and accordingly greatly increasing the working life of the wire cloth.

It is to be mentioned additionally that with the invention hereof, I provide improved water retaining areas between the adjacent warp wires of the pair so as to provide improved lubricity characteristics.

By the use of a combination of relatively thin steel warp wires in pairs and single relatively thick non-ferrous weft wires, the Woven wire cloth exhibits improved capacities for floating and sliding on the water film normally present on the top surfaces of the suction boxes of the papermaking machine and offers improved wearing qualities against the rubbing and wearing contact with the adjacent surfaces of said suction boxes.

A thinner wire offers the advantage that it drains faster, it being theorized that the openings through the wire being shorter, the water obviously drains faster therethrough.

The non-ferrous materials of the weft strands offer a much lower specific gravity than the stainless steel materials of the warp strands, not to mention a lower coefficient of friction, to the end that, when and as lubricated by a film of water, the wire is subjected to a greatly reduced abrasive action when passed over a fixed surface. The wire cloth herein taught will have a longer life than conventional cloth because the weft knuckles are much longer, there being less metal to wear before cracking occurs, and less fracture of the knuckles 1n weaving.

Tl e longer knuckles on the top side of the cloth will leave less pronounced wire marks in the sheet of paper. The

, cloth has a greater tensile strength than the customary type of cloth, as the warp wires are subjected to less damage in weaving.

in actual practice, it has been found that paper formed on the wire cloth of this invention has a smoother surface than the same grade of paper formed on wire cloths of I By having the top knuckles of ordinary construction. the weft wires in approximately the same horizontal plane as the top knuckles of the warp wires, and by broadening the said weft wire knuckles incident to their bending around the lower warp wire knuckles, there is greater supporting surface for the paper pulp and less opportunity.

for the knuckles to protrude and becomeembedded in the fiber mat, so as to leave indentations 1n the surface of the paper. The resultant paper web, qualitywise, is greatly improved by the present invention "And furthermore, the life of the fabric is increased for several reasons. In the first place, the Weft wire makes it possible by flattening the bends thereof during weaving,

. where they cross beneath the warp wires, to elevate them well above the bottom bearing surface of the fabric thus confining the wear to the warp wires and avoiding any longer radii to produce longer knuckles, or knuckles having longer bearing surfaces, acting like sled runners to minimize friction and wear. Finally the reduced crimp in the warp wires permits of the use of harder wire, or wire having a higher modulus of elasticity, and therefore of longer wearing quality.

The weft wires may be said to be relatively deformable by making them of a relatively softer material so that they automatically flatten at the knuckle bends or points or intersection with other wires during the weaving operation, the degree of flattening and the positioning of the knuckles depending on the tension, the alloy, the force of blow struck by the reed, and the diameter of the weft wire.

These foregoing objects and other incidental ends and advantages will in part be obvious and apparent and will in part be more fully pointed out as the nature of the invention is better understood in the progress of the disclosure below. To the end of attaining these objects and advantages and others hereinafter reasonably appearing, it will be explained that the invention consists substantially in the combination, construction, configuration, location and function of parts, as herein described in detail.

It will be apparent, however, that the physical embodiment delineated, albeit the preferred exemplification, is only exemplary of but one of the multiplicity of ways in and purposes for which the principles of the invention may be employed. Same is submitted as a best known embodiment of the invention in accordance with the patent statutes and is given with a view to illustrating and explaining the precise nature of the principles of the invention and their embodiment for practical use, in order that others skilled in the art to which the invention pertains may be enabled to adapt and modify them in numerous variations and modifications, each as may be best adapted to the conditions of any particular use.

The characteristic features which I consider to be novel with my invention, as to its construction and organization and as to its methods of manufacture will be better understood from a consideration of the following detailed description forming a part of this specification, when read in conjunction with the illustrations in the accompanying drawings, wherein like characters of reference are employed to designate like or corresponding parts throughout the several views, and in which:

FIG. 1 is a plan view of a portion of woven Fourdrinier wire showing pairs of warp strands in close contact with each other in the plane of the woven wire;

FIG. 2 is a transverse cross-sectional view of the woven wire shown in FIG. 1 along the line 2-2; and

FIGS. 3 and 4 are graphical tabulations showing the tensile of typical wire cloths before and after oscillation flexing respectively.

With continued reference now to the drawings which illustrate a typical and preferred embodiment of the invention for the purpose of disclosure and form a part of this specification, I have shown a wire cloth illustrated as being of a twill weave type, although it will be understood that this invention is not limited to a twill weave and could be applied to any other forms of weave, such as regular weave, or any other special weave, such as double chain weave, or triple chain weave.

The endless rotating woven Fourdrinier wires or metal cloths of present-day papermaking machines are normally woven in a twill weave where each weft wire passes alternately over two warp wires and over one warp wire, the intersection of weft with warp wires being advanced by one warp wire at each successive pick.

In three shaft twill, known as modified long crimp, two shafts are interchanged after each weft is heat into place. A common threading sequence of the heddles is #1 (front shaft), #2 (middle shaft) and #3 (back shaft). The placement of the warp wires to get the long crimp for the wearing surface of the wires would be, in terms of the opening and crossing of the sheds, a repetitive sequence as follows: Front shed up Middle and back down Middle shed up Front and back down 1 4 Back shed up Front and middle down In suchthreading, the twill follows a pattern to the right and this for the reason that, as one continues to weave, there is more-resistance on the front. shed than ou the middle andback, and this resistance diminishes" resistance to pressure from the weftbeing beat into "place, all so as to createa highly desirable condition of as one progresses to the middle and back sheds, an allimportant consideration to be remembered when weaving with a pair of stainless wires in parallelism. I

When weaving'with a single wire in each shaft, the direction of the twill pattern, if threaded in, as above, would be to the right. If two wires are in parallelism andelose to one another and if they are'threaded in'the foregoingsequence, the twill pattern would also be to the right. 7

In this twill threading of the heddles, with a single wire or with double wires, the resistance by the warp, when beating up the Weft, diminishes from the front to the back, shed. This means that the weft will be less deformed, a feature common to this type of threading,no

matter what material is used for the warps.

1 knuckle.

locking in the weft and ahighly favorable knuckle design on both the top and bottom of the finished woven wire, and further tocreate a desirable conditiomin that, the

weft is pushed upward to thesame plane as the top warp This condition improves the quality of the formed sheet. The top knuckle of the warpthas a longer radius, which, combined with the highly placed weft,

gives a better and more adequate support to the fibers in the web during formation. The lower, knuckles also offer -a distinct advantage from a standpoint of wear. I

With one warp wire in each pair offering less, resistance to pressure, the shape-of the knuckles and their placement in the lattice,"actually placesone ahead of the other to allow more wearing surface than a single wire both lengthwise and crosswise. Just as important, the unworn .radius ofthe wires allows water lubrication from the stock being formed. V

The laying in of the non-ferrousweft, and its position in the lattice, influences the overall thickness of the wire.

vByreducing the overall caliper of the cloth, I am able 1 to closethe mathematical open area or drainage clearance between the warp and weft'wires a highly. desirable con- However, the combination of what is being used in the warp and weft makes an all-important difference. V a

The layed-in pattern of the weft in an all stainless steel woven .wire would be different from the pattern in an all non-ferrous woven wire, and more significantly, when a combination of stainless steel warps and non-ferrous wefts -water'that-is extracted from the'forming web.

'dition because of the fine fiberswhich pass through in the It also .helps decrease the work hardening ofthe stainless steel 'warp wires because the flexing of finished cloth does not ,dis turbthe interlocking wires, the cloth in and of itself is used, the pattern of the weft is decidedlydiiferent from p 7 either pattern. When two small diameter stainless steel warp wires parallel to one another are woven in combination with a non-ferrous weft, the pattern and' shape of being more flexible.

On all semi-twill weaves using round warp wires, the

beat, or number of weft wires per inch, are usually less than the'warp wire count. To have an equal number the knuckles onboth the top and bottom of the wire change, aswell as the layed-inpattern of the weft.

When a monofilament stainless steel warp wire, of a size common to the mesh being woven, is employed in combination with a non-ferrous weft, the interlocking of both in the latticeis undesirable. When the finished wire is run on a papermaking machine, the stainless steel warp work hardens, and, because of a poor locking, of'the lat- ,tice, the wire gets sleazy! Also, the work hardening of the warp eventually causes breaks and holes in the cloth. When two smaller-diameter parallel warp wires I are used, they flex more easily, do not work harden so rapidly,

and, when used .in combination with a non-ferrousweft, f

contribute to a more perfect latticewhich will not loosen when run on a paper making machine. a F

The, wire cloth, according to the exemplary embodiment shown herein, comprises pairs of warp wires and single weft wires, the upwardly crimped knucklesof boththe count.

I When using two'small round wires. in parallel, the beat For instance, in sixty mesh Because of the smaller diameter wires of stainless steel, the number of weft wires in the beat, can be increased beyond the-warp mesh. For. example, 'a comparable wire to .the above conceivably could 'have one hundred and twenty warp wires, said warp wires beingin pairs, and

45, 'sixty-four weft wires.

i low or. above the warp count allowing greater opportunity The flexibility whi'ch'I offer makes it possible to go befor making more grades of paper with th'e same warp The usual practice, in weaving semi-twillwires with a single round warp wire, is. to have theweft wire larger than the warp. The finer the beat, the smaller the weft warp and weft wires'providing the upper paper'formation surface, and the downwardly bent knuckles providing the" lower wearing surface; The :warp wire is preferably a stainless steel wire, and thejweft wire is preferably a rolled or drawn bronze wire which is annealed before weaving, or a brass wire. V r 1 I It is customary, when using a single wire warp thread up,,to have one wire in each harness on each'shaft and one wire per dent in the reed. As an example, inthecase of 60 mesh, there would be 20 wires on each shaft and 60 wires per inch in the reed. 'Contrariwise, when' two wires in parallel are used in the warp on 60 mesh,

there would be 40 wires oneach shaft and .120 wiresper inchin the reed; The threading in the reed, how

ever, is two wires per dent.

In weaving with the double wires, the 'wires, being separated in the heddles but, close together in. the reed,

would influence, the ultimate shape of the knuckles. 7 Having a. previously alluded to the resistance of one warp wire to another on each shaft, it: will be obvious that, when two wires are used in parallel and are threaded in as earlier described, one wire 'in each pairhas less warp should control or predominate .the weft.

wire. I In some. instances, the warp and weft are the same diameter, but this is the exception-rather than the rule. When using double wires in the warp, the same rule applies, but the variation up or down in the weft diameter and count is greater. 1 1

Stainless steel wire has a greater tensile strength under elongationthan brass wire, and this factor is of importance in the sucesesful' weaving of the; wire mesh according to my invention. In the proper weaving of the wire, the I The stronger warp wires permit of; beating the weft wires up to a finerinesh, the warp wires being highly flexible and directly taking the punishment of strains created in operational use. 'The'weft wires, which are shaped by-and follow gthe action of the-warp wires, only indirectly take, the strain imposed'by the beating up operation, and should not be such as to overcome the'predomin'ance or control of the warp wires, Where both the warp and weft are of the same material, asfor instance when they are both of brass, this control is lost to a certain extent, as neither the jwarp nor'the' weft will predominate over the other.

V The dimensions of the Warp wire are proportioned with respect to the 'weft ,wire diameter, the width being such as to provide a relatively wide paper formation and wear surface and the thickness being such as to permit a fine beat up of the weft, and at the same time allow the knuckles of the weft, with a lesser deformation in the crimping of the weft than in the warp, to come into or tive thinness of the warp wires, it will be seen, allows beating up a large number of weft wires per inch, while their relative width when considered in pairs gives an area equivalent to or greater than that of the largest round warp wire permissible.

The cross-sectional width dimension of the double warp wires is approximately twice the thickness dimension, and as the spaced crest of the two wires provide a bridging support for the weft knuckles, the latter will have relatively long flat surfaces in the upper and lower surface planes of the woven wire, thus producing a relatively fiatter type of weave in which the paper formation and wear surfaces of the warp wires are increased from line contact surfaces, as is the case when the knuckles are formed over single circular cross-section warp wires, to surface contact areas substantially corresponding in length to the distance between the crests of the double warp wires. This is of particular advantage at the beginning of the use of the wire as wide contact areas are present both before the knuckles are worn down and after wearing down, so that an approximately uniform wear surface is maintained throughout the life of the wire.

The knuckles of the double warp wires are increased in the warp direction by being formed over the weft wires and are increased in the weft direction by the double crests of each knuckle. The two directional flat knuckles of the warp as well as the two directional wide knuckles of the weft produce a paper formation surface in which the fibers will be supported by flat contact, as distinguished from the point contact with wires having circular crosssection warp and single circular cross-section weft wires. At the same time, the fine beat up of the weft provides a smooth surface which will support the paper stock without the usual tendency to turn down into the mesh and clog it, Without sacrificing this support, the mesh openings may be of adequate size to provide full drainage.

The double warp also disposes double the number of weft knuckles on the wear side and as these have substantially flat surfaces in the weft direction the wearing life will thereby be greatly increased.

The flat knuckles of the warp as well as the fiat knuckles of the weft produce a paper formation surface in which the fibers will be supported by flat contact, as distinguished from the point contact with wires having circular cross section warp and weft. At the same time, the fine beat up of the weft provides a smooth surface which will support the paper stock without the usual tendency to turn down into the mesh and clog it. Without sacrificing this support, the mesh openings may be of adequate size to provide full drainage.

The fine beat up of the weft also disposes more knuckles on the wear side and as these have fiat surfaces the wearing life will not only be greatly increased but the wear will be substantially uniform throughout the life of the wire. The knuckles of wires formed with circular cross-section warp and weft wires have point contact when first in use so that there is a 'very rapid wear during the beginning of the run of the wire.

The wire according to a preferred embodiment of my invention has flat knuckles both in the warp and the weft, and latter being produced by their being crirnped over the flat surfaces of the pairs of warps.

By crimping the weft knuckles over the flat surfaces of the warp, the bending being about the spaced corners formed between the flat top and bottom surfaces and the side surfaces, substantially flat weft knuckles are produced having a greater weft knuckle surface contiguous to the plane of the projected warp knuckles than would be the case if the weft knuckles were formed about single circular cross-section, warp wires.

'The warp wires while providing a much greater tensile strength are at the same time more flexible than circular single cross-section warp wires, so that they may be operated at high speed over rolls for a considerably greater time than heretofore before fatigue sets in.

While the mesh openings are shown as approximately square it will be understood that, by reason of the fine beat up of the weft permitted by my invention, these openings may have a dimension between the weft wires shorter than between the warp wires.

The wire cloth partly shown in FIG. 1, is formed of double warp strands and single weft strands and is illustrated as having a three-leaf twill weave.

The longitudinally-extending war-p threads or strands, formed of steel, are delineated by reference numeral 1 and are provided in pairs laid in side-by-side contact for each mesh. They are laid in close contact with each other in the horizontal plane of the woven wire.

The transversely-extending weft wires of the fabric, formed of a non ferrous metal or a plastic, are delineated by the reference numeral 2.

In FIG. 2, I have shown a cross-sectional view of the fabric for purposes of illustrating that the surface points of the longitudinally-extending warp wires 1 as well as the transversely-extending weft wires 2 are located in a single plane.

The steel warp strands are preferentially of a certain diameter and the non-ferrous or plastic weft strands are preferentially of a diameter in excess of the said certain diameter.

The wire cloth, according to the exemplary embodiment shown, comprises double warp wires of circular cross-section arranged in side-by-side relation, replacing the usual single circular cross-section warp Wire and single weft wires of circular cross-section. The upwardly crimped knuckles of both the warp and weft wires provide the upper paper formation surface, and the downwardly bent knuckles provide the lower wearing surface.

FIGS. 3 and 4 are graphical tabulations showing the tensile of typical wire cloths before and after oscillation flexing, respectively.

Each of the wires was subjected to continuous machine oscillation and flexing some 4000 times. It will be observed that the useable stretch in the .60 mesh double filament of the invention remains virtually unchanged after oscillation flexing, while the useable stretch in the mono filament wires was drastically reduced.

The mono filaments had little or no useahle stretch after reaching the yield point, while such was not the case with the double filament wire hereof.

It is believed that the gist of the invention will be clearly understood from the foregoing disclosure and accordingly, further analysis thereof at this point is considered unnecessary, as I have, in accordance with the provisions of the patent statutes, described the construction and principle of operation of my invention together with the apparatus which I believe to represent the best embodiment thereof, to the end that others can, by applying current knowledge, readily adapted it for various applications without omitting features which, from the standpoint of prior art, fairly constitute essential characteristics of its generic and/ or specific aspects.

I therefore particularly point out and distinctly claim as my invention:

1. Three-leaf twill-weave metal cloth for paper machines characterized by the fact that in the longitudinal direction it consists of two stainless steel warp threads of circular cross-section extending in the same direction parallel to each other per mesh while in the transverse direction it consists of a single non-ferrous weft thread of circular cross-section per mesh, the metal strands of the pairs of warp threads being in contact with each other in the plane of the wire cloth, the warp threads being of smaller diameter than the diameter of the weft threads and the wanp threads being located withinthe upper and lower outerhori-zontal planes of :the wirecloth, V t

2. In an endless *Fourdrinier wire for paper machines comprising a woven mesh of warp and weft strands, each of circular crosesection; the warp strands of the said woven mesh being laid in pairs, the strands of the said pairs of war-p strands being made of a steel and the weft strands being of a non ferrous material, the warp strands V I wire, and the weft strands being compressible so that they are somewhat flattened or deformed at the points'of intersection with the warp strands. Y

3. Woven wire fabric for paper making machines comprising intenwoven warp and Weft shutes,'each comprising a pair of stainless steel warp wires and a single non-ferrous weft wire, with knuckles produced in both the warp and weft wires, the warp wires being carried over one and, 7 under a plurality of weft shutes of substantially circular, cross-section, the warp wires being of substantially cir- 'cular cross-section elongatedin one dimension, said elongated dimension being parallel to the plane of the Woven ;wire fabric whereby the weft knucklescross the elongated elongated faces, the'pair of warp wires of each shute being I arranged sideeby-side, whereby the weft knuckles cross the spaced crests. of said warp wires and have their outer projecting surfaces substantially co-extensive transversely with the spaces between said crest.

References Cited by the Examiner v UNITED STATES PATENTS 1,337,053? 7 4/20 Dreyling -139- -425 1,794,624 3/31 Kastner 139 425.s

2,062,773 12/36 Weber '139-42s.s 2,088,447- 7/37 Specht 139 425.s 2,132,252 7 10/38 Weber 139 42s.s 2,511,540 6/50 'Osterheld 139-425 2,569,764 10/51 J'onas, 1'39-f-42 5 3,143,150 8/64 nuchanan 'fln fltns 139 42s.5

WILLIAM J. STEPHENSON, Primary Examiner. ,NEDW-IN BERGER, Examiner. j I s 

1. THREE-LEAF TWILL-WEAVE METAL CLOTH FOR PAPER MACHINES CHARACTERIZED BY THE FACT THAT IN THE LONGITUDINAL DIRECTION IT CONSISTS OF TWO STAINLESS STEEL WARP THREADS OF CIRCULAR CROSS-SECTION EXTENDING IN THE SAME DIRECTION PARALLEL TO EACH OTHER PER MESH WHILE IN THE TRANSVERSE DIRECTION IT CONSISTS OF A SINGLE NON-FERROUS WEFT THREAD OF CIRCULAR CROSS-SECTION PER MESH, THE METAL STRANDS OF THE PAIRS OF WARP THREADS BEING IN CONTACT WITH EACH OTHER IN THE PLANE OF THE WIRE CLOTH, THE WARP THREADS BEING OF SMALLER DIAMETER THAN THE DIAMETER OF THE WEFT THREADS AND THE WARP THREADS BEING LOCATED WITHIN THE UPPER AND LOWER OUTER HORIZONTAL PLANES OF THE WIRE CLOTH. 